MAP (Mapping of Address and Port) is technology that assigns a set of functions to be executed on a MAP-enabled CPE device (or customer edge router (CE)) and a Border Relay (BR) to provide IPv4 address sharing by using IPv6. Examples of MAP are described in the Internet Engineering Task Force (IETF) Internet Drafts entitled “Mapping of Address and Port with Encapsulation” <draft-ietf-softwire-map>, by Troan et al., and “Mapping of Address and Port using Translation (MAP-T)” <draft-ietf-softwire-map-t>, by Li et al. The key characteristics, in a MAP-T form, are that:                i) the CE router performs a “port-restricted stateful NAT44+stateless NAT46” operation, e.g., where a NAT44 function converts an IPv4 address to another IPv4 address and TCP/UDP port (network address translation, “NAT”), such as in accordance with the IETF' s Request for Comment (RFC) RFC2663, and where a stateless NAT64 function converts, such as in accordance with RFC6145, is extended to allow stateless mapping of IPv4 and transport layer port ranges to IPv6 address space; and        ii) the BR performs a modified stateless NAT64 operation, which allows the BR element to be realized with superior performance and scalability as opposed to stateful carrier-grade NAT (CGN) solutions.        
Many operators attempting to deploy MAP are currently struggling to get the MAP-T CE function implemented. In particular, the MAP-T CE function requires a modification of (existing) NAT44 functionality and the addition of stateless NAT64 and also associated configuration options (e.g., MAP DHCPv6 options) besides IPv6. All of this occurs across a wide variety of existing devices and configurations, where some may not be upgradable to IPv6, thus requiring a change/upgrade to new devices (having wired or wireless uplinks). These technical challenges translate to a bottleneck for MAP deployment and exacerbated IPv4 exhaustion (that is, running out of uniquely assigned IPv4 addresses).